# Pulmonary Vascular Resistance (PVR) Calculator

Determines vascular resistance based on pressure difference and blood flow in pulmonary circulation.

You can read more about the variables involved and the calculation in the text below the tool.

The pulmonary vascular resistance (PVR) calculator estimates an important characteristic of pulmonary circulation, which is vascular resistance in dynes-sec/cm5.

VR is a hemodynamic variable useful in the management of pulmonary and cardiovascular conditions.

PVR measured in dynes-sec/cm5 = 80 x (Mean Pulmonary Arterial Pressure in mmHg – Left Atrial Pressure in mmHg) / Pulmonary Flow in L/min;

Normal PVR is between 20 and 130 dynes-sec/cm5.

Mean Pulmonary Arterial Pressure
Left Atrial Pressure
Pulmonary Flow
* In most cases pulmonary flow is equivalent to cardiac output
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Steps on how to print your input & results:

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.

## PVR explained

This pulmonary vascular resistance (PVR) calculator estimates vascular resistance in the pulmonary circulation based on arterial and atrial pressure difference and pulmonary blood flow.

There are three variables to be specified, as described in the table below:

 Variable Measurement units Description Normal values Mean Pulmonary Arterial Pressure mmHg, cmH2O, kPa, atm or psi Input to the pulmonary blood circuit. 10 – 20 mmHg Left Atrial Pressure mmHg, cmH2O, kPa, atm or psi Output of the pulmonary circuit at the place where blood is transferred to the left atrium. 6 – 12 mmHg Pulmonary flow L/min, mL/min In most cases, pulmonary flow is equivalent to cardiac output. 4 – 8 L/min

Vascular resistance is measured in dynes-sec/cm5, but can also be expressed in mmHg-min/L, measurement known as hybrid reference units or Wood units.

Normal PVR is between 20 and 130 dynes-sec/cm5.

The PVR formula is:

PVR measured in dynes-sec/cm5 = 80 x (Mean Pulmonary Arterial Pressure in mmHg – Left Atrial Pressure in mmHg) / Pulmonary Flow in L/min

There is also a simplified formula that provides PVR in mmHg-min/L:

PVR measured in mmHg-min/L = (Mean Pulmonary Arterial Pressure in mmHg – Left Atrial Pressure in mmHg) / Pulmonary Flow in L/min.

PVR is a characteristic of the pulmonary circulation and represents the difference of pressure across the pulmonary circuit, divided by the rate of blood flow going through it. This definition and the usual calculation have been explored above.

The main physical determinants of resistance to blood flow in a blood vessel are:

■ Vessel length (L);

■ Vessel radius or circumference (r);

■ Blood viscosity (η).

■ Vasoconstriction (decrease in blood vessel diameter and increase in PVR);

■ Vasodilation (increase in blood vessel diameter and decrease in PVR).

PVR is influenced by the tone in the small resistance arterioles (vessels with diameters between 100 and 450 µm) and by the resistance in pre-capillary arterioles (even smaller diameters).

PVR also depends on lung volume and was determined to be at its lowest at functional residual capacity (FRC).

Causes of high PVR or pulmonary hypertension include:

■ Pulmonary vascular disease;

■ Pulmonary embolism;

■ Pulmonary vasculitis;

■ Hypoxia.

Lower than normal PVR is most commonly caused by dysfunction in one of the following: calcium channel blockers, delivery of O2, isoproterenol or aminophylline.

## Example of a PVR calculation

When:

■ Mean Pulmonary Arterial Pressure = 16 mmHg;

■ Left Atrial Pressure = 13 mmHg;

■ Pulmonary flow, cardiac output = 5.5 L/min.

The pulmonary vascular resistance = 80 x (16 – 13) / 5.5 = 43.64 dynes-sec/cm5.

## References

1. Barratt-Boyes BG, Wood EH. Cardiac output and related measurements and pressure values in the right heart and associated vessels, together with an analysis of the hemo-dynamic response to the inhalation of high oxygen mixtures in healthy subjects. J Lab Clin Med. 1958; 51(1):72-90.

2. Baim D. (2006) Grossman's Cardiac Catheterization, Angiography, and Intervention. Lipincott Williams & Wilkins 7th ed.

3. Skimming JW, Cassin S, Nichols WW. Special Article: Calculating Vascular Resistances. Clin. Cardiol. 1997; 20, 805-808.

Specialty: Cardiology

System: Cardiovascular

Objective: Determination

Type: Calculator

No. Of Variables: 3

Abbreviation: PVR

Article By: Denise Nedea

Published On: April 19, 2017

Last Checked: April 19, 2017

Next Review: April 19, 2023